Different.
Well this game has been done tons of times, but you added somthing to it, which was a great idea. Theres so much you could do with this though, why not levels? And different enimies other then those circles things. What about different colors? Or customization. Or even some planets in the background. There is so much more you could do with a submission like this, and I hope you do, this could be one of the best games there are if you just add some extra things to it. Average game.